html{   
    width: 100%;   
    height: 100%;   
    overflow: hidden;   
    font-style: sans-serif;   
}

body{
    background-image: linear-gradient(#2F4F4F, #000000);  
}
#topic{   
    position: absolute;   
    top: 50%;   
    left:50%;   
    margin: -150px 0 0 -150px;   
    width: 300px;   
    height: 300px;   
}   
#topic h1{   
    color: #fff;   
    text-shadow:0 0 10px;   
    letter-spacing: 1px;   
    text-align: center;   
}   
h1{   
    font-size: 2em;   
    margin: 0.67em 0;   
}   

.but{   
    width: 250px;   
    min-height: 100px;   
    display: block;   
    background-color: #458B74;   
    border: 0px;
    box-shadow: 0 2px 5px 0 #ffffff; 
    color: #fff;   
    padding: 9px 14px;   
    font-size: 20px;   
    line-height: normal;   
    border-radius: 10px;   
    margin: auto;   
 }


